1. The Field of the Invention
This invention relates to spinal vertebral implants and methods and instruments for inserting the implants between spinal vertebrae in order to achieve spinal fusion.
2. The Prior State of the Art
When tissues between spinal vertebrae, also known as intervertebral disks, become herniated or otherwise injured, the disks can compress against nerves associated with a particular location on a spinal column. Such injuries are common in the lumbar vertebrae, for example, and can cause extreme pain to a patient suffering from such injuries.
One treatment common among medical providers to treat such injured intervertebral disks is a spinal fusion. In typical spinal fusion procedures, a portion of a vertebral disk or the entire vertebral disk is removed from between adjacent upper and lower vertebrae and the upper and lower vertebrae are fused to form a single spinal structure. The fusion of the vertebrae can alleviate the pain and discomfort associated with injured disks and frequently does not result in significant loss of bending capability.
A variety of different treatment modalities have been developed to perform such spinal fusions. Examples of typical treatments include the use of a spinal implant placed between two adjacent vertebrae. Typical implants include those made from bone, often harvested from a cadaver, for example. Following the removal of the intervertebral disk, the spinal implant is placed between the vertebrae and fuses over time with the vertebrae, eventually forming a single fused member. Typical implants can also comprise a metallic material, for example.
A variety of different approaches have been developed to use implants to achieve spinal fusion. For example, one approach employs a cage-like metallic structure in which fragments of bone are placed. The cage is mounted between adjacent vertebrae and is designed to maintain distraction between vertebrae, thus maintaining the vertebrae a desired distance apart from each other. The bone fragments foster fusion between the adjacent vertebrae. However, the cage-like structures merely act as distractors and do not fuse between the vertebrae. Instead, only the bone fragments foster fusion between the vertebrae. Thus, the space used by the cage is not used to foster bone growth and fusion. Furthermore, if bone growth does not occur through the holes for any reason, the implants merely serve as distractors, that is, placeholders that maintain spaces between adjacent vertebrae, rather then fostering fusion therebetween. The use of metal cages also introduces a foreign object into the disk space where fusion is to be obtained.
Other implants comprise harvested bone without a cage member. Typical such implants include implants comprising first and second bone pieces coupled together, for example. However, such coupled pieces can fail to fuse to each other, or can form a false joint which can eventually result in decreased fusion or the lack thereof.
There is therefore a need in the art for an improved spinal fusion implant that can be mounted between adjacent vertebrae and achieve fusion therebetween. There is also a need in the art for an improved method for placing spinal fusion implants between adjacent vertebrae. There is also a need in the art for instruments capable of achieving improved methods for implanting spinal implants.